Method for continuously cutting away pieces from a continuously moving endless material and apparatus for performing same

ABSTRACT

To shorten the processing time in modern plants for cutting away pieces or sections from a continously moving endless material, e.g. a glass strip, one after the other by flying cutting the cutting bridge carrying the cutting device ( 6 ) is accelerated until at a speed within a predetermined tolerance range of the feed speed of the continuously running endless material. Then the cutting bridge speed is synchronized for each piece or section to be cutaway and the cutting away of each piece or section takes place after the synchronization. To attain a very high precision cutting the spacing of the front cut edge formed when the previous piece or section is cut away from the cutting device is measured by means of an image-taking device ( 7 ) prior to cutting away of the next piece or section. Then the measured spacing is compared with a set value for the spacing and the speed of the cutting bridge is synchronized or fine tuned according to the comparison prior to cutting away the next piece or section.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method for continuouslycutting off successive pieces or sections from a continuously movingendless material by flying cutting by means of a cutting apparatus ordevice accelerated to the speed of the endless material, which issynchronized for each piece or section. It also relates to a cuttingapparatus for performing the method.

[0003] 2. Prior Art

[0004] Products in various industrial fields are often availableinitially in the form of continuously moving endless material, typicallyas a band or strip. These fields include e.g. flat glass manufacture,steel, aluminum or other metal production or processing fields, certainparts of the plastic industry (for example foil manufacture) and areasof the food industry. In each application the continuously moving bandor strip must be cut into predetermined lengths, pieces or sections. Theline of the cutting is generally perpendicular to the motion directionof the endless material, i.e. the belt or strip edge.

[0005] In order to avoid interruption of the continuous motion of theendless material and so that processing time is not increased, thecutting away of the pieces or sections is performed in a known manneraccording to the principle of “flying sawing”. According to theprinciple of “flying sawing” a portal or frame, in which a cross-cutslot is provided with a cutting tool, the so-called cutting bridge, isaccelerated to the speed of the endless material. As soon as the speedof the endless material is reached, cross-cutting is initiated. Thus theendless material is cut so as to form a rectangular piece or section ofthe endless material. Subsequently the bridge is moved back into itsinitial position.

[0006] The adjustment of the speed of the cutting bridge to the speed ofthe endless material occurs typically by means of a controller. Thecontroller establishes a certain predetermined set speed (V-set) for thedrive system of the cutting bridge. The controller must also set theexact time point at which the synchronous motion is started. Adifference between the actual speed (V-act) and the set speed (V-set) ofthe cutting bridge or an inexact starting time for the cutting causesinaccurate cutting. The cutting speed of the cutting bridge is thegreatest source of factors interfering with the accurate cutting away ofthe pieces or sections from the endless material.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide an improvedmethod for cutting away successive pieces or sections from acontinuously moving endless material of the above-described type, whichcuts the pieces or sections with an accuracy in the {fraction (1/100)}mmrange.

[0008] It is also an object of the present invention to provide animproved cutting apparatus for performing the improved method accordingto the invention.

[0009] The method according to the invention for continuously cuttingaway successive pieces or sections from a continuously moving endlessmaterial by flying cutting by means of a traveling cutting deviceaccelerated to the speed of the endless material, which is synchronizedfor each piece or section, comprises the steps of:

[0010] a) producing a pre-control speed value for pre-controlling acutting device travel speed to bring it within a synchronization rangeof a feed speed of the continuously moving endless material;

[0011] b) pre-controlling the cutting device travel speed according tothe pre-control speed value until it is within the synchronizationrange; and

[0012] c) then generating a control signal for fine regulation of thecutting device travel speed; and

[0013] d) controlling the cutting device travel speed by means of acutting device travel speed controller according to the control signalfor fine regulation so that each piece or section is cut to apredetermined piece or section length;

[0014] wherein the actual value of a distance of the front cut edge ofthe endless material from which a previous piece or section was cut tothe cutting device is measured, a set value of the distancecorresponding to the predetermined length of the next piece or sectionto be cutaway is compared with this actual value and the differencebetween the set value and the actual value is calculated, the speed ofthe traveling cutting device within the synchronization range is thenfine-tuned or controlled by increasing it or decreasing it by means ofthe speed controller according to the comparing when there is adifference and the next piece or section is cut away when the set valueagrees with the actual value.

[0015] The above-described objects of the invention are also attained inan apparatus according to the invention that includes a conventionaltraveling cutting bridge, which has an elongated carriage that travelsin the motion direction of the endless material and a transverselytraveling carriage with a cutting tool that is mounted on the elongatedcarriage, which are accelerated for flying cutting by drive means andare synchronized to the feed speed of the continuously moving endlessmaterial.

[0016] According to the invention the apparatus has a camera devicemounted on the cutting bridge at a predetermined distance from thecutting tool, which corresponds to a length of the next piece or sectionto be cut away, and control means for the drive means are provided. Thecontrol means comprises means for analyzing image signal produced by thecamera device and for producing control signals for the drive means forcontrolling the acceleration of the cutting bridge according to theanalysis of the image signals.

[0017] The principal features of the invention are that the speed of thecutting device is brought within a synchronization range of the speed ofthe endless material and after that the speed of the cutting device isfine-tuned or adjusted according to the length of the given piece orsection. Because of these features the accuracy of the cut piece orsection is within {fraction (1/100)}mm.

[0018] According to a preferred embodiment of the inventive method boththe distance of the front cut edge from the cutting tool is measured andthe subsequent fine control of the speed synchronization are alsoperformed during the cutting of the endless material. After the cuttingis complete they are interrupted or halted until activation orinitiation of a following cutting process. Because of this feature ahigh precision of the cutting process is also maintained during thecutting of the endless material.

[0019] The control expense and effort can be limited according to apreferred embodiment of the method according to the invention when thedistance of the front cut edge from the cutting tool is measured and thesubsequent fine control of the speed synchronization are started as soonas the cutting device is within the tolerance range for the cutting tobe performed.

[0020] An especially simple control of the cutting away process can beobtained according to a preferred embodiment of the invention by aposition control, in which the front cut edge of the endless material isimaged on a camera device moving with the cutting device, the measuredposition of the image of the cut edge is compared with a position setvalue and the speed of the cutting device to be synchronized issubsequently controlled according to a deviation of the measuredposition from the position set value and the cutting away is initiatedor started when the measured position agrees with or corresponds to theposition set value.

[0021] In order to provide a rapid fine control, it is performeddigitally and iteratively in successive steps according to a preferredembodiment of the invention. Also an analog control is conceivable.

[0022] According to another embodiment the apparatus according to theinvention is formed so that the camera device is ahigh-speed-partial-scan camera and the controller is a digitalcontroller, in which associated image analysis software is provided.This sort of arrangement guarantees the necessary rapid detection of thefront edge of the continuously moving endless material and the rapidfine control.

[0023] An analog controller can also be employed.

[0024] According to another embodiment of the apparatus a camera devicecomprising a camera with integrated processor is provided. In this casethe external image processing software and associated processor can bedispensed with.

[0025] An especially fine control is possible when the camera device isa streaking camera with connected comparing device in an alternativeembodiment of the apparatus according to the invention.

[0026] In a further embodiment of the apparatus according to theinvention an illuminating device is arranged on the cutting bridge toprovide better optical detection of the front cut edge of the endlessmaterial. The illuminating device illuminates the view field of thecamera device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The objects, features and advantages of the invention will now beillustrated in more detail with the aid of the following description ofthe preferred embodiments, with reference to the accompanying figures inwhich:

[0028]FIG. 1 is a front plan view of a cutting bridge according to theinvention for flying cutting of pieces or sections from a continuouslymoving endless material;

[0029]FIG. 2 is a side view of the cutting bridge shown in FIG. 1;

[0030]FIGS. 3 and 4 are respective flow charts showing complementaryparts of a method for flying cutting away of sections or pieces from thecontinuously moving endless material according to the inventionincluding fine adjustment for accurate cutting the sections or pieces tolength;

[0031]FIG. 5 is a schematic block diagram of an apparatus for performingthe method illustrated in the flow charts of FIGS. 3 and 4; and

[0032]FIG. 6 is a detailed view of the endless material during a cuttingprocess according to the method of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033]FIGS. 1 and 2 show a cutting bridge 1 for continuously cuttingaway pieces or sections from a continuously moving endless material bycracking or scoring the material. The continuously moving endlessmaterial is a glass strip 2. The glass strip moves out from the drawingplane in the front view of the cutting bridge shown in FIG. 1. The pieceor section can be broken off mechanically along the score line. The“scoring” performed in this “score-break-method” in the embodimentdescribed here is part of the “cutting” according to the presentinvention.

[0034] The cutting bridge has stationary portals 3, which are connectedwith each other by means of longitudinal supports 3 a and cross members3 b. An elongated carriage comprising carriage parts 4 a and 4 b ismovable longitudinally, i.e. in the motion direction of the glass strip2, along the longitudinal supports 3 a. The elongated carriage parts 4 aand 4 b are connected with each other by a transverse support 5. Atransversely traveling carriage 5′ is mounted on the transverse support5 extending perpendicular to the motion direction of the glass strip 2,i.e. in the scoring direction. This traveling carriage 5′ carries ascoring or cutting tool 6 for scoring the glass strip 2 at apredetermined cutting or score line. The desired section or piece isobtained by breaking it off at the predetermined score line. The cuttingbridge has a suitable drive system, preferably a three-phase alternatingcurrent servo-drive or linear drive for moving it in the direction ofmotion of the glass strip 2.

[0035] The cutting bridge is itself known and is thus not described infurther detail here. It operates in a known way so that during motion ofthe glass strip 2 the cutting tool 6 is accelerated to the speed of theglass strip from its initial position for cutting each section or piece.Also it is synchronized to the speed of the glass strip before the glassstrip is scored or cut. The synchronization of the speeds of the cuttingtool and the moving endless material is maintained during the scoring,i.e. during the cutting away of the section or piece. The cutting bridgemoves back into its initial position after each scoring or cuttingevent.

[0036] According to the invention an image-taking device 7 is fixed orattached to the cutting bridge. However its position is adjustable andof course so that its spacing in the motion direction of the glass strip2 from the cutting tool 6 corresponds to the length of the section orpiece being cut from the endless material. This image-taking device 7 isthus moved at the synchronized speed. The image-taking device 7 detectsor images the score last made during the scoring and breaking process,or the cut edge when the glass strip is cut through e.g. by means of alaser beam, when the next piece or section is in the set range. Theimage-taking device 7 has a window defined by set marks, whichcorresponds to the position of the imaged edge or score, when thedistance between it and the cutting or scoring tool corresponds exactlyto the length of the desired section or piece.

[0037] The image-taking device 7, preferably a high-speed partial-scancamera or also a CCD-surface camera, is employed together with a digitalcontroller and associated image processing software according to themethod set forth in the flow chart in FIGS. 3 and 4. The images from thecamera are analyzed by means of the image processing software. The imageprocessing software then produces a “faster” or “slower” signal as aguiding parameter or control signal that is input to the servo-drive ofthe longitudinal carriage according to whether the image of the cut edgeor score is one side or the other of the window. An analog controllerproduces a suitable “faster” or “slower” control signal accordingly.Because of that the drive accelerates or brakes the cutting bridge. Thisoffset speed can be parameterized. After that a camera image is receivedor evaluated and the speed of the cutting bridge is correspondinglycorrected if necessary. The controller corrects the sped during thesynchronization of the current bridge until the controller or the imageprocessing software signal that the cut edge or the score is in thepredefined window. This sort of control process typically lasts only afew fractions of a second.

[0038] The above-described signal serves as a start signal for thethree-phase alternating current drive of the transversely travelingcarriage 5′ for initiating the transverse cutting by the cutting tool 6.During the scoring or cutting the set position is further controlled.Optionally the camera device does not travel in the transverse cuttingdirection, but only in the direction of motion of the glass strip.

[0039] After the end of the scoring or cutting the control is halted andthe cutting bridge travels with both carriages back into the initialposition.

[0040]FIG. 5 shows a block diagram of the apparatus for performing themethod according to the flow charts shown in FIGS. 3 and 4, includingthe essential parts of the apparatus, as well as a description of howthe parts cooperate.

[0041] The block 9 represents the drive means for the elongated carriage4 a, 4 b. The drive means 9 is connected with a drive controller 10.This drive controller 10 supplies the set value for the speed to thedrive means 9 and obtains the actual value of the drive speed from it.

[0042] The drive means 9 for the elongated carriage 4 a,4 b is coupledby means of a camera drive system 11, e.g. a spindle, with animage-forming means, i.e. with the camera device 7. The output signalsof the camera, including the image data, are fed to a camera controller12, which analyze these data. The camera device 7 is accelerated by thedrive means 9 for the elongated carriage, until moving synchronouslywith the motion of the glass strip 2. As soon as the motion issynchronized, the drive controller 10 gives the “start measurement”signal to the camera controller 12.

[0043] The camera controller 12 analyzes the image data from the cameradevice 7. It determines the relationship of the cutting track 13 at thefront cut edge of the endless material to a reference mark 14 given bythe tolerance range 14. This process is illustrated in the detailedviews of the camera image field 15 shown in FIG. 6 (from the section Ataken from FIG. 5). The camera controller 12 sends control signals forchanging the speed of the elongated carriage in the drive controller 10depending on the relative position of the cutting track 13 on the glassstrip 2 and the reference mark 14. The drive controller 10 moves theelongated carriage faster or slower in the motion direction of the glassstrip according to the measured deviation of the cutting track 13 fromthe reference mark 14. The drive controller 10 guides the drive means 9for the elongated carriage with the aid of this speed input.

[0044] The detailed successive views of the camera field 15 illustratedin FIG. 6 show the relative position of the cutting track 13 at threetime points. At time point t1 the cutting track 13 is located outside ofthe tolerance range forming the reference mark 14. The camera speed isthen changed so that the cutting track 13 approaches ever more closelyto the reference mark 14 (at time point t2), until at the time point t3it is located within the tolerance range of the reference mark 14. Thecamera controller 12 feeds the “start cutting” signal to the drive means16 for the transversely traveling carriage 5′ for the cutting tool 6.

[0045] An illuminating device 8 that illuminates the camera view field(FIG. 1) is mounted on the cutting bridge for improved detection of thescoring track or the cut edge. In the case of the above-named cameratypes the illuminating device 8 is preferably a LED, which emits lightin the red spectral region. However other illuminating devices, such ase.g. “cold light”, are conceivable. Other arbitrary camera types can beused instead of the above-described CCD area camera.

[0046] Known cameras with integrated processors that are programmablecan also be used. If these known cameras are employed, it is notnecessary to provide a separate processor and image-processing software.

[0047] The fastest detection of the actual position of the front cutedge is possible with a streaking camera with hardware in the form of aconnected comparator and with an appropriately fast drive controller forthe elongated carriage and the transversely traveling carriage.

[0048] Besides the advantages already described above the existingcutting bridge can be equipped without further effort with the apparatusaccording to the invention. This feature expands the applicability ofthe present invention.

[0049] Generally the present invention is applicable to any endlessmaterial from which sections or pieces must be continuously cut off.

[0050] The disclosure in German Patent Application 100 00 469.5-45 ofJan. 7, 2000 is incorporated here by reference. This German PatentApplication describes the invention described hereinabove and claimed inthe claims appended hereinbelow and provides the basis for a claim ofpriority for the instant invention under 35 U.S.C. 119.

[0051] While the invention has been illustrated and described asembodied in an apparatus and method for continuously cutting off piecesfrom a continuously moving endless material by flying cutting duringmotion of the endless material, it is not intended to be limited to thedetails shown, since various modifications and changes may be madewithout departing in any way from the spirit of the present invention.

[0052] Without further analysis, the foregoing will so fully reveal thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic or specific aspects of thisinvention.

[0053] What is claimed is new and is set forth in the following appendedclaims.

We claim:
 1. A method for continuously cutting away successive pieces orsections from a continuously moving endless material by flying cuttingduring the movement of said endless material moving at a predeterminedfeed speed and said flying cutting being performed by means of atravelling cutting device accelerated synchronized to said predeterminedfeed speed for each of said pieces or sections to be cut away from theendless material, said method comprising the steps of: a) producing apre-control speed value for pre-controlling the cutting device to bringthe travel speed of said cutting device within the synchronization rangeof said feed speed of said endless material; b) after thepre-controlling of step a), generating a automatic control signal forfine regulation of the cutting device travel speed; and c) controllingthe cutting device travel speed according to the automatic controlsignal for fine regulation so that each of said pieces or sections iscut to a predetermined piece or section length; wherein the controllingof the cutting device travel speed is performed for each cutting away bya process including measuring an actual value of a distance of a frontcut edge of the endless material, from which a previous one of saidpieces or sections was cut, to the travelling cutting device,determining a set value for said distance according to a predeterminedlength of a next one of said pieces or sections to be cut following theprevious one, comparing the actual value with the set value, increasingor decreasing the cutting device travel speed within the synchronizationrange according to the comparing of the actual value and the set valueuntil the actual and set values agree and cutting off the next one ofthe pieces or sections to be cut when the set value agrees with theactual value.
 2. The method as defined in claim 1 , wherein saiddistance of the front cut edge to the traveling cutting device (6) ismeasured and said controlling of the traveling device cutting speedaccording to the control signal for fine regulation are performed duringthe cutting away of the next one of the pieces or sections, but areinterrupted after said cutting away, until starting a subsequent cuttingaway process for a following one of the pieces or sections.
 3. Themethod as defined in claim 1 or 2 , wherein said distance of the frontcut edge is measured and the controlling of the traveling cutting devicespeed according to the control signal for fine regulation are started,as soon as said distance of said front cut edge of the endless materialto the traveling cutting device (6) is within a tolerance range forperforming the cutting away of the next one of the pieces or sections.4. The method as defined in claim 1 , further comprising imaging saidfront cut edge of said continuously moving endless material by means ofan image-taking device (7) moving with the traveling cutting device (6)and comparing a position of an image of said front cut edge with aposition of a set mark of the image-taking device, subsequentlycontrolling said traveling cutting device speed according to a deviationof said position of said image of said front cut edge from said positionof said set mark and starting said cutting by means of said travelingcutting device when said position of said image corresponds to said setmark.
 5. The method as defined in claim 1 , wherein said controlling ofthe treavling cutting device speed according to said control signal forfine regulation is performed digitally and iteratively.
 6. An apparatusfor continuously cutting away successive pieces or sections from acontinuously moving endless material by flying cutting, saidcontinuously moving endless material moving at a predetermined feedspeed and said flying cutting being performed by means of a travelingcutting device accelerated to said predetermined feed speed andsynchronized with each of said pieces or sections to be cut away fromthe endless material, said apparatus comprising a cutting bridge (1)including an elongated carriage (4 a,4 b) mounted for traveling in amotion direction of the continuously moving endless material; drivemeans (9) for moving said elongated carriage (4 a,4 b) at apredetermined feed speed in said motion direction; a transverselytraveling carriage (5′) mounted on said elongated carriage so as to bemovable transverse to said motion direction of the continuously movingendless material; a cutting device (6) mounted on said travelingcarriage (5′) for cutting away said pieces or sections insynchronization with said feed speed of said endless material; drivemeans (16) for operating said cutting device (6) to cut away said piecesor sections from said endless material in synchronization with said feedspeed; an image-taking means (7) arranged at a predetermined distancefrom said cutting device (6), said predetermined distance correspondingto a predetermined length of said pieces or sections to be cut away,said image-taking means (7) comprising means for generating imagesignals; and a controller (10) for controlling said drive means (9) forsaid elongated carriage (4 a,4 b) according to said image signals fromsaid image-taking means (7).
 7. The apparatus as defined in claim 6 ,wherein said image-taking means (7) comprises a high-speed partial-scancamera and said controller (10) is a digital control device containingan image-analysis software program.
 8. The apparatus as defined in claim6 , wherein said image-taking means (7) comprises a camera and processorintegrated in said camera.
 9. The apparatus as defined in claim 6 ,wherein said image-taking means (7) comprises a streaking camera withconnected comparator.
 10. The apparatus as defined in claim 6 , whereinsaid cutting bridge includes an illumination device for illuminating aview field of the image-taking device (7).